A series of US children's textbooks on Islam contains misleading and inflammatory rhetoric about the religion, inaccurately portraying its followers as hostile and deserving of suspicion, according to a US Muslim civil liberties group.

"The overall theme of the books is that Muslims are inherently violent, that Islam is a second-rate religion and that one should be wary of Muslims in any society," said Moein Khawaja, the chapter's civil rights director. "These books do not fulfil the mission of a school, which is to educate."

Among dozens of examples cited by Khawaja, the book Muslims in America says: "Some Muslims began immigrating to the United States in order to transform American society, sometimes through the use of terrorism." Elsewhere, a picture of two smiling Muslim girls in head scarves appears on a page subtitled "Security Threats".

It was not immediately clear where the series was being used, either in classrooms or libraries. But Khawaja said complaints from council chapters across the country led him to believe it was on bookshelves in about two dozen states.

The publisher, based in the Philadelphia suburb of Broomall, did not return a request for comment.

The research institute president Harvey Sicherman said he was mystified by the reaction to the series and the two examples were taken out of context.

The photo placement was inadvertent, he said, and the caption in no way implied the girls were security threats. The quote about Muslim immigration to America was accurate, Sicherman said. "Well, yes, some people did come to the United States to commit terrorism, and I don't know how one can quarrel with that sentence."

Sicherman said a representative from the institute would attend the Muslim group's news conference to learn more.

Khawaja said the problem went beyond isolated sentences to what he described as the series' overarching anti-Islamic tone and message. "A book isn't just a set of quotes – it's a conclusion you walk away with."

He noted a chronology in the book Islam in Europe started with 1988 and listed 10 events, seven of which involved extremist Muslims participating in bombings, hijackings or other violence.

"Muslims have been in Europe for thousands of years," Khawaja said. "This is ridiculous."